Field
The subject matter of the present disclosure relates to the field of molecular constructs for T-cell receptors, as well as methods of making and using these T-cell receptor molecular constructs for treating pathologies such as viral infection or cancer.
Description of Related Art
T-cell receptors (TCRs) are important elements of adaptive immunity, as they specifically recognize antigenic peptides bound to MHC proteins (peptide/MHC complexes or pMHCs) on cell surfaces. The binding of the TCRs to the antigenic peptides and the MHC proteins is responsible for initiating immune responses against the presented antigen. The TCR-pMHC interaction is notable in health and disease, especially in the areas of transplantation, autoimmunity, and as a target for therapeutics for infectious disease and cancer. Clinical trials using adoptive transfer of genetically engineered T-cells, in which tumor-specific TCRs have been transduced, have shown promise in the treatment of certain cancers such as metastatic melanoma and synovial cell sarcoma (PMID: 16946036, PMID: 19451549, PMID: 21282551).
TCRs are proteins that recognize ligands composed of two or more distinct components; characteristically this ability is referred to as dual recognition. Typically, TCRs possess only low to moderate affinity for their ligand, an antigenic peptide bound and presented by an MHC protein, also referred to as a peptide/MHC complex or pMHC. Because of the weak binding affinity of TCRs, much research has been focused on engineering TCRs with higher binding affinities to be used as therapeutics in cancer and infectious diseases (e.g., PMID: 17947658, PMID: 18997777). The aim of that research is to enhance (or equivalently, strengthen) binding affinity and thus increase the potency of the immune response. Common techniques for increasing binding affinity include in vitro evolution using yeast or phage display. While these techniques work to enhance the binding affinity of TCRs by introducing random mutations, there are concerns about maintaining the necessary specificity to the antigenic peptide and impacts from off target effects of the enhanced-affinity TCRs (PMID: 17947658, PMID: 25070852). For example, the modifications introduced into an affinity-enhanced HLA-A1-restricted MAGE-A3-specific TCR used to treat metastatic melanoma caused the death of patients due to TCR cross-recognition of an antigen from the cardiac protein, titin (PMID: 23770775).
Computational structure-guided design of T-cell receptors has been used to enhance binding affinity in a controlled fashion (e.g., PMID: 24550723, PMID: 25070852). The research, however, is still focused on modifications that enhance or strengthen binding to the pMHC. The unresolved problem that remains using these conventional approaches is the non-specific binding and cross-reactivity of the TCR, a problem which may be further enhanced with a high affinity construct. A need continues to exist in the art for development of improved artificial/synthetic T-cell receptor constructs that reduce and/or eliminate non-specific binding and cross-reactivity, while preserving at least good binding affinity and specificity towards a selected, therapeutically relevant target peptide bound by a MHC protein. Some reports define good binding affinity as that described with a KD in the low double-digit micromolar range when measured by a technique such as surface plasmon resonance.
Despite the above and other approaches, the medical arts remain in need of materials and methods for enhancing the specificity, and hence the focus, of therapeutic moieties, including cells, TCRs, anti-cancer agents, drugs, and antibodies, for improved treatment of diseases, such as viral infections and cancer.